<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
	</head>
	<style>
		#box{
			width: 300px;
			height: 300px;
			margin:0 auto;
			position:relative;
			background-color: #ccc;
			
		}
		#son{
			width: 200px;
			height: 200px;
			position:absolute;
			left:50px;
			top:50px;
			background-color: skyblue;
			display: flex;
		}
		#son-1{
			flex: 1;
			background:gold;
		}
		#son-2{
			flex: 1;
			background:blueviolet;
		}#son-3{
			flex: 1;
			background:tan;
		}
	</style>
	<body>
		<div id="box">
			<div id="son">
				<div id="son-1"></div>
				<div id="son-2"></div>
				<div id="son-3"></div>
			</div>
		</div>
	</body>
</html>
